With rapid development of hybrid vehicles that combines gasoline and electric power recovering driving power of the vehicles to get steady electric power for electric motors equipped in the vehicles has become a heavy focus in research and development projects among car producers. At present the commonly adopted technique of electric power generation through recovering the driving power mainly focuses on providing a power generator on a vehicle to generate electric power when the vehicle is moving at a speed greater than a preset value to charge a battery set to provide electric power for activation and operation of the electric motors. However, traffic jam in urbane area takes place frequently nowadays, and most vehicles often are in a low speed condition and cannot move at a higher speed to start the power generator to charge the battery. As a result, the battery could not save enough electric power to support operation of the electric motors.
To address this issue, Applicant proposed a technique of recovering driving power during sliding or braking of vehicles that was disclosed in China patent publication Nos. CN103072493A, CN102101430A and China patent No. CN201656546U. While the aforesaid technique can recover driving power to generate electricity during the vehicles in a sliding or braking condition, the vehicles are at a lower speed state, and the rotor in the power generator driven by the wheel axle also is decelerating, hence spinning speed difference between the rotor and a stator of the power generator is not significant. As a result, power generation efficiency of the power generator is lower. It still leaves a lot to be desired in terms of power generation efficacy.